A method is known for example from the Patent Application 10 2007 009 545.9 (2007P03983 DE) submitted to the German Patent and Trademark Office, is referred to as a modified backscatter technique. Until now, this technique has been used only for relatively small areas.
DE 102 36 943 B4 and, in a similar manner, EP 0 720 539 B1 disclose methods which are used to identify dangers caused by scatter currents which can occur on the track installations of direct-current railroads. In the process, for example, faults on voltage flashover protection devices are identified.
Normally the rails are used as the electrical return path for direct-current railroads. The rails are therefore insulated from ground, that is to say from the ground. Specifically, the aim is that no current should flow from the rails through the ground into surrounding conductive structures. Structures such as these may be parts of building foundations or tunnel installations, or else pipeline systems. When structures such as these are composed of metal, the current flow can lead to corrosion. The insulation between the rails and the ground may, however, become damaged over the course of time or may be electrically bridged in some other way, as a result of which scatter currents can enter the ground and the structures that are endangered.
In order to allow such scatter currents to be identified, a plurality of measurement points for electrical voltages between the rail and the ground are arranged along the railroad line, according to DE 102 36 943 B4. The measured values measured there must then be transmitted to an evaluation center. In addition, according to EP 0 720 539 B1, potential differences are measured between the rail and the ground, and these measured values are then transmitted to a control center. Normal radio signals are used for this purpose.